The open-end spinning process is now widely practiced. In this process a flow of discrete fibres is fed by an air stream into a rotating spinning chamber and the fibres are deposited on an inner surface of the chamber. From that surface they are picked up by a tail end of yarn which is continuously withdrawn from the top or bottom of the chamber, the action forming a continuous yarn which has a true twist.
Many forms of apparatus are now known for forming the open-end spinning process, but without exception the yarns produced by this process have a very harsh feel, so limiting their end uses. In a number of cases the degree of cleanliness that can be achieved in the yarn also leaves something to be desired.
The open-end spinning process introduces a true twist into the yarn, and the twist can be varied by varying the speed of the drive to the open-end spinning unit. GB-A-1174041 proposes that the twist introduced at the open-end spinning unit can be modified, either increased or reduced, while taking up the yarn from the open end spinning unit and forming it into a package, for example utilising yarn take up means that may be spinning rings and travellers, caps, flyes and the like. This proposal is purely and simply designed to facilitate the production of a yarn with a given degree of twist, and has very little effect on the yarn properties known to be disadvantageous in open-end spun yarn, namely harshness and lack of cleanliness.
These disadvantages do not necessarily exist in other types of spun yarns. Other spinning techniques include traditional ring spinning, jet spinning and friction spinning. Although in some properties any of these may be superior to open-end spun yarns, nevertheless their properties may be capable of enhancement.
The present invention seeks to modify a spun yarn in such a way as to improve the properites of the yarn.